1. Field of the Invention
This invention relates in general to coating apparatus and in particular to apparatus for coating a web with a liquid coating composition. More specifically, this invention relates to a novel apparatus for multiple stripe coating of a web.
2. Description of the Prior Art
A variety of techniques are known for multiple stripe coating of a web, that is, for applying a coating composition to a web in the form of a plurality of stripes each of which is separated from an adjacent stripe by a region which is uncoated. Such coatings can be applied, for example, by the use of a coating roll provided with a plurality of grooves corresponding to the stripes to be applied. Another form of apparatus for use in multiple stripe coating is described in British Pat. No. 384,293. This patent describes an apparatus comprising a coating trough provided with openings adjacent to the apex of the trough, means for mounting the trough with the apex contacting the web to be coated, and means for tilting the trough to vary the extent to which the web partially covers the openings and thereby vary the amount of coating composition applied. An alternative type of multiple stripe coating apparatus is that of Canadian Pat. No. 770,540 which describes an apparatus comprising an applicator head having a plurality of bores formed therein and a web-engaging surface in the form of spaced lands which separate the bores from one another. Other types of striping apparatus are disclosed in U.S. Pat. No. 3,032,008 which describes a device comprising a multiplicity of aligned nozzles defining at least two different sets with the nozzles in each set being connected to a supply of coating composition under pressure; in Russian Pat. No. 413,053 which describes a slide hopper adapted for stripe coating by the provision of shims or inserts within the slots and guide rails which fit tightly against the slide surfaces; and in U.S. Pat. No. 3,886,898 which describes an apparatus comprised of block-like members equipped with a plurality of orifices and separated by thin flat dividers. While these devices are all capable of applying a plurality of stripes to a web, difficulties are frequently encountered in achieving precise control of stripe width and registration and the apparatus is often unduly complex and difficult to maintain. It is toward the objective of avoiding such difficulties and providing a simple and effective multiple stripe coating apparatus that is capable of providing a high degree of accuracy in stripe width and registration that the present invention is directed.